A woman in the US has rapidly gained weight to the point of being obese, following a faecal microbiota transplant (FMT) from an overweight donor.

The woman received the transplant to treat a recurring Clostridium difficile infection, which causes diarrhoea, nausea, and sometimes colitis - inflammation of the inner lining of the colon that can lead to rectal bleeding. Because this is the kind of infection that tends to return more often than n...